Cam follower type rocker arms for internal combustion engines pivot about a fixed point in response to rotation of the cam. The rocker arm thereby activates a valve of the internal combustion engine. During assembly of the internal combustion engine, the valve train, which comprises the valve, valve spring, rocker arm, overhead cam and lash adjuster, are assembled to the cylinder head at a location remote from the remainder of the internal combustion engine. The cylinder head, with the valve train components attached thereon, is then transported to the location of the remaining portion of the internal combustion engine for assembly. During this transportation, the location of the rocker arm relative to the valve stem may move as the cylinder head is jostled in place. Relocating the rocker arm relative to the valve stem may result in increased assembly cost.
U.S. Pat. No. 4,539,953 discloses a rocker arm which is bifurcated at the valve actuating end, and which straddles the valve stem so as to locate the rocker arm relative to the valve stem. However, a problem with this approach exists in that a heavy mass at the actuating end which requires relatively more energy to move. In addition, the valve spring must be stronger to compensate for the added weight. All of this reduces engine efficiency and ultimately reduces fuel economy.
In addition, the rocker arm of U.S. Pat. No. 4,539,953 is a complicated design from a manufacturing standpoint. That is, after the rocker arm is formed, the valve guide at the valve actuating end must be machined during a secondary operation whereby a grinding tool of appropriate size must be guided through the bifurcated end of the rocker arm to smooth the surface. This may require special tooling and fixturing with the result being increased manufacturing cost. Also, the sides that straddle the valve stem must be relatively large, and thus heavy, to withstand this machining operation.
Further, it is known that directing lubricating oil toward the cam/rocker arm interface is desirable to reduce friction. To provide this lubricating oil, previous designs have incorporated a channel within the rocker arm that directs lubricating fluid from the pivot end to the cam/rocker arm interface. This channel is necessarily formed at an angle not perpendicular relative to any surface of the rocker arm and again may require special fixtures and increased machine setup time, thereby increasing manufacturing cost.